#include"stack.h"

//栈的初始化
void STInit(ST* ps)
{
	assert(ps);
	ps->arr = NULL;
	ps->capacity = ps->top = 0;
}

//判断栈是否为空
bool StackEmpty(ST* ps)
{
	assert(ps);
	return ps->top == 0;
}

//入栈
void StackPush(ST* ps, STDataType x)
{
	assert(ps);

	//判断空间是否充足，不足增容
	if (ps->capacity == ps->top)
	{
		int newcapacity = ps->capacity == 0 ? 4 : 2 * ps->capacity;
		STDataType* tmp = (STDataType*)realloc(ps->arr, newcapacity * sizeof(STDataType));
		if (tmp==NULL)
		{
			perror("realloc fail!");
			exit(1);
		}
		ps->arr = tmp;
		ps->capacity = newcapacity;
	}
	//空间足够
	ps->arr[ps->top++] = x;
}

//出栈
void StackPop(ST* ps)
{
	assert(ps);
	//判断栈是否没有数据，是空栈
	//assert(ps->arr)
	assert(!StackEmpty(ps));

	--ps->top;
}

//取栈顶元素
STDataType StackTop(ST* ps)
{
	assert(ps);
	assert(!StackEmpty(ps));

	return ps->arr[ps->top - 1];
}

//获取栈中有效元素个数
int STSize(ST* ps)
{
	assert(ps);
	return ps->top;
}

//栈的销毁
void STDestroy(ST* ps)
{
	assert(ps);
	if (ps->arr)
	{
		free(ps->arr);
	}
	ps->arr = NULL;
	ps->top = ps->capacity = 0;
}
